A dual wet clutch has an input hub intended to be rotationally integrated with an engine flywheel fastened to the crankshaft of the engine, and two clutches each having an input disc carrier rotationally connected to the input hub, an output disc carrier rotationally connected to one or the other of the two input shafts of a gearbox, and a multiple-disc assemblage that is intended to transmit a torque between the input disc carrier and the output disc carrier of said clutch when said clutch is in its engaged position.
One of the input shafts of the gearbox, rotationally connected to the output disc carrier of the one of the clutches, corresponds to the odd-numbered ratios of the gearbox, while the other input shaft, rotationally connected to the output disc carrier of the other clutch, corresponds to the even-numbered ratios. In order to perform a change of ratio, one of the clutches is therefore displaced from its engaged position to its disengaged position, while the other clutch is displaced from its disengaged position to its engaged position. A dual clutch of this kind thus allows a change of ratio with no interruption in torque.
The existing art, and in particular the document US 2015 0219167, discloses a dual wet clutch of this kind in which the input disc carriers are supported by a hub that is mounted rotatably on a control shaft fastened on the housing of the gearbox. Each of these clutches is controlled by a respective piston that is mounted on the hub, axially movably between a disengaged position and an engaged position in which it presses the discs of the multiple-disc assemblage of said clutch against one another in order to transmit a torque between the respective input and output disc carriers. Each of the pistons is disposed between an activation chamber, which when it is pressurized allows the piston to be displaced from its disengaged position to its engaged position, and a balancing chamber that allows compensation for the dynamic pressure induced by centrifugal force. The control shaft has a plurality of oil supply conduits that are each connected to one or more respective holes configured in the hub, said holes each opening into one of the activation or balancing chambers. Dynamic seals are disposed between the control shaft and the hub, and allow the conduits of the control shaft to be separated in sealed fashion. In addition, the compensation chambers permit fluid to circulate to the multiple-disc assemblages so as to ensure lubrication and cooling of said multiple-disc assemblages.
A dual clutch of this kind is not entirely satisfactory, since the presence of dynamic seals has the effect of generating friction that induces a drag torque which is responsible for excessive energy consumption.
Also known, in particular from DE 10 2014 212805, are dual wet clutches that are actuated by means of a hydraulic control system having a housing intended to be fastened on the gearbox, having two concentric annular chambers and two annular pistons axially movable respectively in one and the other of the two annular chambers. Each of the pistons carries a rotating stop that is in abutment against a force transmission member interacting with one or the other of the two clutches so as to displace said clutch between a disengaged position and an engaged position upon movement of the piston within its respective annular chamber. A control system of this kind allows the drag torque to be limited, and consequently offers satisfactory energy consumption performance.
The fluid intended for cooling of the clutches is supplied, however, through one of the input shafts of the gearbox, which makes production of the gearbox more complex.